The present invention relates to a servovalve for air-conditioning systems with terminal apparatuses formed of fan-convectors, inductors or the like, with contemporaneous supply of hot and refrigerated water by means of four pipes, two for the delivery and two for the return, known as xe2x80x9cfour pipe systemsxe2x80x9d.
It is known that, at present, each terminal apparatus of this kind of system associated to two heat exchangers, one of which is passed through by hot water and the other one by refrigerated water, both being provided with a servovalve in order to control the water flow from the relevant delivery pipe. A generally electronic thermostatic device senses the temperature of the environment wherein the apparatus or xe2x80x9clocal unitxe2x80x9d is installed and controls the two valves sequentially, by means of a rectilinear movement of a control means, such as a shutter. If the sensed temperature tends to rise above the calibration value, the xe2x80x9ccoldxe2x80x9d heat exchanger controlling valve opens; on the contrary, if the temperature tends to lower, the xe2x80x9chotxe2x80x9d heat exchanger controlling valve opens. It is absolutely necessary that, when one of the valves is open, the other one be closed in order to avoid the contemporaneous operation of the two heat exchangers resulting in mixing of the two water flows and in a waste of energy. However, for various reasons, such a sequence may fail to occur, owing either to a thermostatic device defect or to a defect of the valve sealing.
It is also known that, due to overall size reasons, in the present local apparatuses the xe2x80x9chotxe2x80x9d heat exchanger has a much smaller heat exchange surface than the xe2x80x9ccoldxe2x80x9d one, thereby the hot water being fed must have a high temperature, which results in a considerable thermal dispersion from the pipes and does not allow the use of alternative energy sources such as heat pumps or solar collectors, by which particularly high temperatures cannot be obtained.
Therefore, the first object of the present invention is to eliminate one of the two valves and one of the two heat exchangers for each local apparatus of a xe2x80x9cfour pipexe2x80x9d conditioning system, thus reducing the equipment""s cost and avoiding that contemporary liquid flows having different temperatures occur in the apparatus, with notable economic advantages due to both a certain reduction in the equipment""s cost, and the resulting energy gain.
Another object of the present invention is obtaining a better proportionality between valve stroke and liquid flow, with respect to the one obtainable with the rectilinearly moving valves of the prior art, as well as the independence of the valve operation from the hydraulic pressure of the circuit, with a simplification of the automatic control, since controlling two valves in sequence is no longer necessary, in addition to a simplification of the hydraulic connections.
A further object of the present invention is allowing to change in a particularly simple way the control valve characteristic, which is generally indicated with Kv, corresponding to the water flow rate in m3/h for a 1 bar pressure drop. In fact, by the valve according to the present invention it is possible to obtain different Kv values with the same valve, by adapting the characteristic thereof to that of the circuit that it has to control. Finally, it is possible to use alternative energy sources for heating the water that, with the valve according to the present invention, does not necessarily have to reach particularly high temperatures.
Said objets and advantages are obtained by means of a six-way rotating valve whose structural features are specified in claim 1.
Particularly preferred embodiments are obtainable through the features of the claims dependent from claim 1.